The video signals present on a video magnetic tape are read by a magnetic transducer in close contact with the tape. The transducer has a gap and as the tape passes this gap a changing flux pattern is created in the magnetic transducer. This changing flux pattern causes a changing current in windings on the magnetic transducer. This current is the video signal and it can be transformed into a voltage, amplified and conditioned as desired. One limitation which delayed the use of magnetic tapes for video signals was the relatively poor frequency response of the magnetic tape and the corresponding transducer.
A major technical breakthrough occurred when the rotating transducer principle was successfully applied to reading and writing magnetic tape signals. When the transducer is rotated counter to the direction of the tape, the apparent tape speed is proportionally increased, and thus the frequency performance of the tape is enhanced to allow video signals to be recorded on magnetic tape. This, together with the discovery that a lower frequency signal can be successfully frequency modulated by a much higher frequency, improved quality of magnetic tapes, helical scanning, azimuth recording and other improvements have resulted in high quality consumer video tapes and cassette recorders.
Since the transducer is rotating, the signals picked up must be transferred to and from this rotating device. Usually slip rings or rotating magnetic transformers are used for this transfer, but these devices are a source of performance limitations. They have poor frequency and impulse response, linearity and fidelity. They attenuate the signal and increase the noise. These limitations affect the signals read from the tape and the signals written on the tape resulting in a double performance loss.